The present invention relates to methods of recording a neural response from neural tissue after it is stimulated. More specifically, the present invention relates to methods for rapidly and accurately recording and processing neural responses.
Modern neural stimulators have the capability of measuring the response of nerve tissue to an electrical stimulus. This involves delivering a stimulus to a nerve through a stimulating electrode and recording, with a sense or recording electrode, the electrical response of the nerve as it depolarizes and repolarizes.
Obtaining a neural response (“NR”) for a particular electrode configuration and thus a particular set of nerves is important clinically to ascertain whether the targeted nerves are, in fact, being stimulated by the implanted stimulator system. It is further important to determine the range of stimulus amplitudes for which the nerve responds. Such nerve response information is used to set the stimulus parameters delivered by an implanted device such as a cochlear stimulator for the deaf. Another application where NR information could be used to help set stimulation parameters is spinal cord stimulation for treating chronic intractable pain. The use of cochlear and spinal cord stimulation systems are well-accepted medical therapies.
Conventional methods for determining NR involve obtaining multiple recordings of neural responses at a particular stimulus amplitude. The multiple recordings are then averaged to provide a more accurate, peak amplitude response. The averaged peaks are then plotted as a function of varying stimulus amplitudes for each electrode configuration. Such a resulting neural response curve is called an “input/output function” or, alternatively, a “growth curve” for a set of nerves stimulated by a particular electrode configuration.
Disadvantageously, the conventional methods of recording NRs often stimulate the same nerve repeatedly over a short duration of time in order to obtain an averaged response. The higher the stimulation frequencies, the more the NR appears to “adapt” resulting in an attenuation of the NR amplitude and thereby introducing inaccuracy in the NR recordings. In addition, the entire recording session often takes too long to complete in the clinical setting because the recordings to characterize the electrode configurations are performed inefficiently.
Accordingly, what is needed is a method for quickly recording and processing NRs, while eliminating inaccuracy caused by adaptation by a target nerve to repeated stimulation.